Renewable Energy Vol. 2, No. 1, pp. 35 39, 1992 Printed in Great Britain.

0960 1481/92 $5.00+.00 1992 Pergamon Press Ltd

W I N D E N E R G Y POTENTIAL OF N I G E R I A

L. O. ADEKOYA a n d A. A. ADEWALE

Agricultural Engineering Department, Obafemi Awolowo University,, Ile-lfe, Nigerm

(Received 24 June 1991 : accepted 15 A ugusl 1991 )

Abstract--Wind speed data for 30 locations in Nigeria were analysed. Annual mean wind speeds and power flux densities were determined to vary from 1.5 to 4.l m/s and 5.7 to 22.5 W/m 2, respectively. The mean maximum power extractable from two hypothetical aerogenerators were determined. The potential uses of wind energy in the country are for electricity generation and water pumping in rural areas.

1. INTRODUCTION

The wind is an inexhaustible resource that can provide significant quantities of energy to support a country's needs. Since earliest recorded history, man has been harnessing the energy of the wind. There is evidence that wind energy was used to propel boats along the Nile River as early as 5000 B.C. [1].

Wind energy utilization in Nigeria is practically non-existent. Three main reasons are responsible. Firstly, when compared globally with other regions of the world, the mean wind speeds in West Africa have been considered to be far below those of other regions [2]. Secondly, fossil energy is available in the country. Thirdly, a large proport ion of electricity is generated by hydroelectric plants.

However, fossil fuel is getting more and more expensive every year, and is not readily available in some remote locations. Also, only the big cities and towns enjoy electric power and most of the rural areas, where over 70% of the population live, are not con- nected to the national grid. Neither do they have independent power generating plants.

It is known that various stationary (non-vehicular) agricultural tasks could be adapted to use wind energy. Principal applications of wind energy in agri- culture are general farmstead power supply (primarily electrical), irrigation pumping, product storage and processing, and water supply for rural communities and animals. Most of these applications will require small wind systems ranging from 10 to 100 kW and perhaps even small wind farms [1].

This work was therefore carried out with the fol- lowing objectives :

(i) to analyse the wind speed data for locations in the country,

(ii) to determine the power flux densities, and the mean maximum extractable power from two hypothetical aerogenerators and

(iii) to determine the potential of wind energy util- ization in Nigeria.

2. WIND SPEED DATA

Wind speed data for 30 locations within the country were obtained from the Nigerian Meteorological Ser- vices, Lagos (Fig. I). The data (Table l) were for periods ranging from 8 to 22 years, and were measured at various heights ranging from 4.9 to 15.3 m. Table 2 shows these facts and some other relevant statistics of each meteorological station shown in Fig. 1. It can be seen that the sites were spread all over the country, and as such the data can be said to be sufficiently comprehensive.

3. WIND SPEED DATA ANALYSIS

3.1. Mean wind speed

Because the data were measured at different heights above ground level, the mean wind speeds at 10 m above ground level were first computed. The effect of different heights on wind speed has been studied by many authors [3, 4], and the relationship for computing the wind speed at a height of 10 m when measurements are taken at heights other than 10 m is given as

[/2 = \ H 2 ] " (1)

where V ~ - wind speed at height H~ = 10 m above ground level, V2 = wind speed at height H2 above ground level, and a = roughness factor.

Assuming ~ = 0.25, the mean wind speeds at a height of l0 m are as shown in Table 3. This table shows that the wind speed regimes in Nigeria are generally weak. The values range from a low of 1.5 m/s

35

36 L. Om ADEKOYA and A. A. ADEWALE

12'

10'

t .v Soekoto ,,...,- .~e ~ . . / 't Kotsino "- . . . . N~uru !

{ / ( _

i 6~sou Kono Moiduguri i"

/ Pof'~m / "'~ (. • Zo r i o ," "

~. YeTwe rY Ka~una Bauchi ~" "? Jos ," J

J I ') .I )

t M~nfle .f'~ / • Bide Y(~O J

i " . . ) I i I tor i n ,t'r # • Ibi /

! Os, ogbo Lo~ojo Hc~kurdi /'; ) . Ibodon / m ) • Ondo m ) ) • Ijebu - Ode . 1 " ..... ~ • o lke je Enugu .,J ". /

Loges ~ - ~ Benin • On,tsho ,.-" ' ~ , Ikom(.

'twain ,' Bight of Benin ~ ~ " ' * / 'or

Bigh t of B i g f r a ~ I

t,o ~o ~o 1~)o t , 12 ° 1~ o

Fig. 1. Map of Niger ia showing the win(] data stations.

in Bida, Ikom and Warri, to a high of 4.1 m/s in Sokoto. Generally, the northern parts of the country (especially north of 10'~N) are windier than the southern parts of the country. These northern locations generally have mean wind speeds of 2.5 m/s and above, while the southern locations have mean wind speeds of less than 2.5 m/s (Fig. 1, Table 3). However, it is to be noted that local terrain features can cause the mean speed to vary considerably over short distances, especially in coastal, hilly, or mount- ainous areas. Therefore, there will be local areas of higher or lower mean wind speed than is shown in Table 3.

3.2. Wind power estimates For any wind stream with speed V (m/s), of cross-

sectional area A (m2), and air density p (kg/m3), the power in the wind, P, (W), is given by [4]

P, = ½pA V3. (2)

However, the theoretical maximum fraction of extracted power is 16/27 or 59.3%. This maximum is called the Betz maximum [4]. The maximum overall efficiencies have been shown to range from 40% for horizontal axis high-speed turbines, to 30% for ver-

tical-axis turbines (e.g. Savonius rotor) and to 15% for multi-bladed horizontal-axis type rotors [4, 5].

In general, for any useful power outputs to be econ- omically considered, the minimum mean wind speed ranges have been variously put at 2.1-3.1 m/s [6] and 2.5-3.5 m/s [2]. Taking 2.5 m/s as the lower limit, and the theoretical maximum power as 59.3% of that given by eq. (2), mean wind power flux densities (W/m z) have been computed for locations with adjusted mean wind speeds of 2.5 m/s or higher. Additionally, mean wind powers that can be extracted from circular areas with diameters of 2 and 4 m have also been computed and are shown in the last two columns of Table 3. Locations with adjusted mean wind speeds below 2.5 m/s have been discountenanced as insignificant sources of wind power.

4. POTENTIAL USES OF WIND ENERGY IN NIGERIA

Since wind energy is free whenever it is available, there are definite economic benefits to be gained by harnessing even the most meagre and highly seasonable wind energy resources available in the different parts of the country• Since the wind speed range for electricity

Wind energy potential of Nigeria

Table 1. Mean monthly wind speeds at measuring heights*

37

Station Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Mean

Bauchi 2.3 2.4 2.6 2.8 2.9 2.4 2.2 1.9 2.0 2.0 2.0 2.5 2.3 Benin-City 1.8 2.2 2.2 2.0 1.9 2.0 2.2 2.4 2.2 1.8 1.5 1.6 2.0 Bida 1.2 1.5 1.9 2.2 1.9 1.7 1.5 1.4 1.3 1.1 1.2 1.1 1.5 Calabar 1.7 2.0 2.1 2.0 2.0 2.0 2.1) 2.1 2.0 1.8 1.7 1.5 1.9 Gusau 3.7 3.9 3.8 3.5 3.7 3.7 3.2 2.5 2.0 1.7 2.9 3.6 3.2 ibadan 1.8 2.4 2.7 2.5 2.4 2.4 2.7 2.7 2.3 t.8 1.4 1.6 2.2 ljebu-Ode 2.0 2.5 2.5 2.5 2.2 2.2 2.3 2.7 2.1 1.6 1.5 2.1) 2.2 lkeja 2.1 2.3 2.4 2.6 2.2 2.2 2.5 2.7 2.4 2.0 1.8 1.9 2.2 lkom 1.2 1.7 2.0 1.9 1.8 1.6 1.4 1.5 1.6 1.5 I. I 0.9 1.5 llorin 1.6 2.0 2.6 2.6 2.3 2.2 2.5 2.5 2.0 1.9 1.7 1.5 2.1 Jos 4.1 4.0 4. t 4.3 4. I 4.2 4.0 3.8 3.5 3.6 4.1 4.2 4.(t Kaduna 3.5 3.2 2.9 3.1 3.0 2.9 2.8 2.7 2. I 1.9 2.8 3.2 2.8 Kano 3.7 3.5 3.6 3.9 4.4 4.6 3.9 3.4 3.0 3.0 3.2 3.5 3.6 Katsina 3.6 4.11 3.2 3.8 4.3 4.6 4.0 3.2 3.0 2.6 2.8 3.3 3.5 Lagos 2.1 2.5 2.7 2.9 2.8 4.6 2.4 2.2 2.2 2.4 2. I 1.8 2.4 Lokoja 1.6 2.0 2.6 2.4 1.9 1.5 1.7 1.6 1.6 1.7 1.7 1.6 1.8 Maiduguri 2.9 3.2 3.6 3.3 3.0 3.2 3.2 2.5 1.8 2.5 3.2 3.0 3.11 Makurdi 2.1 2.5 2.4 3.2 2.6 2.6 2.5 2.5 2.1 2.0 1.9 1.8 2.4 Minna 2.0 2.1 1.7 1.8 1.7 1.6 1.4 1.3 1.3 1.0 1.5 1.8 1.6 Nguru 3.1 3.1 3.0 2.8 2.8 2.9 2.8 2.5 2.2 2.2 2.9 3. [ 2.8 Ondo 1.2 1.7 1.7 1.4 1.3 1.4 1.7 1.7 1.5 1.2 1.0 1.t) 1.4 Onitsha 1.5 1.5 1.8 1.7 1.7 1.7 1.3 1.5 1.6 1.5 1.3 1.4 1.5 Oshogbo 1.2 1.7 2.0 2.0 1.7 1.7 2.0 2.0 1.6 1.2 0.9 1.0 1.6 Port Harcourt 1.9 2.2 2.2 2.1 2.1 2.1 2.I 2.3 2.2 1.9 1.6 1.7 2.11 Potiskum 1.9 2.2 2.4 2.7 3.0 3.1 2.8 2.1 1.8 1.6 1.7 1.7 2.3 Sokoto 4.8 4.4 3.7 3.7 4.2 4.9 4.3 3.3 3.(t 2.9 3.5 4.9 4.0 Warri 1.2 1.4 1.7 1.6 1.5 1.5 1.5 1.7 1.6 1.4 1.3 1.2 1.5 Yclwa 1.7 1.8 2.3 3.1) 3.1 2.7 2.1 1.8 1.7 1.6 1.5 1.5 2. I Yola 1.0 2.5 1.9 2.2 2.1 1.8 1.6 1.6 1.4 1.2 1.0 1.0 1.6 Zaria 3.7 3.2 3.0 3.7 3.6 3.5 2.9 2.5 2.11 2.11 2.7 3.6 3.0

* Measuring heights are shown in Table 2. Source : Nigerian Meteorological Service, Lagos.

generation is 5-6 m/s [7], the most highly practicable potential use of wind energy in Nigeria will be for water pumping for irrigation and domestic use in the rural

areas. The rural water supply application is particularly

more attractive than the irrigation application for two reasons. Firstly, the rural dwellers get their water from unhygienic sources such as rivers, streams and ponds. Generally, water from underground sources are cleaner

than that from surface sources. Secondly, the water requirements during the year for a rural water supply are more or less constant. This implies that the wind pump will be used all the year round. In contrast , the demand of water for irrigation is seasonal, so the wind pump will stand idle during part of the year. Considering the high capital investment involved, this will put the wind pump for irrigation at a high dis- advantage when compared with a diesel pump.

Given the fact that local terrain features can cause the mean speed to vary considerably over short dis- tances, it is not inconceivable that mean wind speeds of 5-6 m/s may be achieved in some localities. If that

is the case. it may be possible to utilize wind energy for electricity generation. However this application

will be in the low power range (less than 10 kW).

5. CONCLUSIONS

The potential o f using wind as a source of energy in Nigeria has been broadly assessed. Using wind speed data from the Nigerian Meteorological Service, it was observed that the northern parts o f the country (especially north of latitude 1 0 N ) are windier than the southern parts of the country. These northern

parts have annual mean wind speeds of 2.5 m/s and above while the southern locations have annual wind speeds of less than 2.5 m/s. Calculations of mean maximum power extractable from two hypothetical aerogenerators of rotor diameters of 2 and 4 m were also made. Potential uses are deduced to be in water pumping and electricity generation using relatively small wind machines with installed capacities of less t h a n 10 k W .

Tab

le 2

. S

om

e re

lev

ant

stat

isti

cs o

f th

e m

eteo

rolo

gic

al s

tati

on

s

Sta

tio

n

Nu

mb

er

of

Lo

cati

on

M

easu

rin

g

yea

rs o

f d

ata

°N

°E

hei

gh

t (m

) co

llec

tio

n*

Bau

chi

10

20

9 47

6.

1 13

B

enin

-Cit

y

6 25

5

30

5.5

21

Bid

a 9

00

5 59

10

.5

18

Cal

abar

4

50

8 15

6.

0 19

G

usa

u

12

12

6 40

6.

1 17

Ib

adan

7

22

3 58

10

.0

21

Ijeb

u-O

de

6 47

3

58

10.0

10

Ik

eja

6 39

3

23

15.3

22

Ik

om

6

00

8 41

9.

9 8

Ilo

rin

8

32

4 34

5.

7 20

Jo

s 9

54

8 53

9.

9 21

K

adu

na

10 2

8 7

25

9.2

22

Kan

o

12

02

8 30

10

.4

20

Kat

sin

a 13

00

7

40

9.2

15

Lag

os

6 25

3

27

13.7

I1

L

ok

oja

7

49

6 44

9.

2 19

M

aid

ug

uri

11

53

13

16

12

.2

21

Mak

urd

i 7

44

8 35

10

.0

19

Min

na

9 39

6

32

4.9

16

Ng

uru

12

53

10

30

6.

0 16

O

nd

o

7 05

4

55

5.5

21

On

itsh

a 6

10

6 47

5.

2 10

O

sho

gb

o

7 50

4

35

10.0

18

P

ort

Har

cou

rt

4 43

7

05

10.0

19

P

oti

sku

m

11

40

11

03

5.5

16

So

ko

to

13

02

5 15

9.

2 18

W

arri

5

31

5 46

9.

6 13

Y

elw

a 10

56

4

54

8.2

18

Yo

la

9 14

12

32

9.

2 22

Z

aria

11

06

7

44

10.0

17

* S

ou

rce

: N

iger

ian

Met

eoro

log

ical

Ser

vice

, L

ago

s.

Win

d e

ner

gy

po

ten

tial

of

Nig

eria

Tab

le

3.

Mea

n

ann

ual

p

ow

er f

lux

dens

itie

s an

d

mea

n

win

d

po

wer

fro

m

circ

ula

r ar

eas*

Sta

tio

n

Mea

n a

nn

ual

M

ean

p

ow

er

win

d s

pee

d

Mea

n

po

wer

fr

om

cir

cula

r at

10

m

a.g.

l,

flux

den

sity

ar

eas

(W)

(m/s

) (W

/m 2

) D

=2

m

D=

4m

Bau

chi

2.6

5.7

17.9

71

.6

Ben

in C

ity

2.

3 B

ida

1.5

--

--

Cal

abar

2.

2 --

--

G

usa

u

3.6

15.2

47

.8

191.

0 lb

adan

2.

2 --

--

--

lj

ebu

-Od

e 2.

2 --

--

Ik

eja

2.0

--

--

Iko

m

1.5

--

--

llo

rin

2.

4 --

--

Jo

s 4.

0 20

.9

65.7

26

2.6

Kad

un

a 2.

9 8.

0 25

.1

100.

5 K

ano

3.

6 15

.2

47.8

19

1.0

Kat

sin

a 3.

6 15

.2

47.8

19

1.0

Lag

os

2.2

--

Lo

ko

ja

1.9

--

--

Mai

du

gu

ri

2.9

8.0

25.0

10

0.0

Mak

urd

i 2.

4 --

--

M

inn

a 1.

9 --

--

N

gu

ru

3.2

10.7

33

.6

134.

5 O

nd

o

1.6

--

--

On

itsh

a 1.

8 --

--

--

O

sho

gb

o

1.6

--

--

Po

rt H

arco

urt

2.

0 --

--

P

oti

sku

m

2.6

5.7

17.9

71

.6

So

ko

to

4.1

22.5

70

.7

282.

7 W

arri

1.

5 --

--

--

Y

elw

a 2.

2 --

--

--

Y

ola

1.

6 --

--

--

Z

aria

3.

0 8.

8 27

.7

110.

7

* S

tati

on

s w

ith

ad

just

ed m

ean

an

nu

al w

ind

sp

eed

s le

ss t

han

2.5

m/s

hav

e n

ot

bee

n c

on

sid

ered

in

the

app

rox

imat

e w

ind

po

wer

cal

cula

tio

ns.

.t-

O

> >

e~

> > > >

Wind energy potential of Nigeria 39

Acknowledgement--The authors are very grateful to the Nig- erian Meteorological Service, Lagos, for assistance rendered in retrieving and releasing the wind speed data to them.

REFERENCES

1. Solar Energy Research Institute, Wind Energy : Technical Information Guide. U.S. Department of Energy (1989).

2. J. Meel and P. Smulders, Wind pumping: a handbook. World Bank Technical Paper No. 101, The World Bank, Washington, DC (1989).

3. A. S. R. Darwish and A. A. M. Sayigh, Wind energy potential in Iraq. Solar Wind Technol. 5, 215 222 (1988).

4. E. H. Lysen, Introduction to Wind Energy, 2nd Edn. Consulting Services Wind Energy Developing Countries (CWD) (1983).

5. D. M. Considine, Energy Technology Handbook. McGraw-Hill, New York (1977).

6. W. Wolde-Ghiorgis, Wind energy survey in Ethiopia. Solar Wind Technol. 5, 341 351 (1988).

7. J. Park, The Wind Energy Book. Cheshire Books, Palo Alto, CA (1981).